The present invention relates to a composite-type ruler enabling an easy drawing of vertical lines, right-angled lines, diagonal lines, and curved lines, as well as a measuring of a horizontal plane of an object. The ruler can also be optionally used in association with a tape ruler.
Heretofore, various types of rulers have been known. For example, there is a composite-type ruler for drawing right-angled lines and diagonal lines forming an angle of 45.degree. therebetween as well as measuring a horizontal plane of an object. The ruler comprises a moveable member having a vertical edge at one side thereof and a diagonal edge at the other side thereof. The moveable member has a guiding groove at the bottom thereof. A straight ruler member is slideably fitted into said guide groove and held at a desired position relative to the moveable member by means of a threaded hole provided at said moveable member and a screw fitted into said hole. In this construction, the screw is likely to release from the hole, thereby causing an inaccuracy in the drawing of right-angled lines or diagonal lines. In this case, a draftsman should again tighten the screw. If the moveable member is required to move with respect to the ruler member, the draftsman should always release and tighten the screw. This work is very cumbersome. Over a long period of use, there is a problem of an inaccuracy in drawing due to the worn states of the screw and the guiding groove.
On the other hand, where parallel lines are to be drawn on a long plate, the following manner has been conventionally utilized. A straight ruler is once placed at one side of the plate. Then, a draftsman marks points spaced a desired distance from one another at said side of the plate, depending upon the scales of said ruler. Thereafter, the ruler is displaced to the other side of said plate and then the above-mentioned work is repeated at said other side of the plate to mark points respectively corresponding to those on said one side of the plate. Then, the straight ruler is transversally disposed on the plate such that respective two points marked at respective sides of the plate and corresponding to each other are aligned on the edge of said ruler in order to draw a line. In this condition, parallel lines can be drawn along the edge of plate, as the ruler is sequentially displaced. This method, however, creates double work for marking a distance between parallel lines. To find accuracy in making points, it is required to compare all points one by one with the scales of ruler. Where incorrectly marked-points are present, the correcting work is troublesome and wasteful in terms of time.